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Guidelines on Windows' Registry safety.

How to backup the Registry.

How to re-install that Registry.

Registry Backup and Reinstall utilities.

Microsoft's Emergency Recovery Utility (ERU).


Windows 95/98 holds important information on software, hardware, and user preferences in a variety of system files: the Registry, Win.ini, System.ini, INF folder, others.

The Registry (system.dat and user.dat) holds vital information and is necessary for running Windows 95/98. This information is stored in three major subgroups called Registry keys. Each is duplicated in the Registry, so you will actually see six groups. The value of each key is set by the software installed, or by information entered.

Many common, sometimes disastrous, Windows 95/98 problems result from faulty data in the Registry. Tweaking the Registry can be dangerous. It can cause failure of Windows 95/98 to start, a lock up, a crash, a program failure. Registry alterations may be useful, or even necessary, but caution is advised.


Many home users are tempted to manually alter the registry.
It can be quite safe to do so. The degree of risk involved depends on the level of understanding, and on competence and precaution.

Any change you make is implemented immediately and without prompting. It is a one way street and you need to know how to get out of it.

There can be no long term damage provide you:
1. Backup a current working version of the Registry
2. Know how to re-install that backup from DOS
If you are unsure of EITHER, then do not interfere with the Registry

ALWAYS backup a WORKING version FIRST

• • • > All changes are final - there is no Undo < • • •


One of the few certainties of life is that the Windows Registry WILL become corrupt at some stage. The result may be a minor hipcup or a total disaster.

Microsoft may have created the problem but it is your computer and it is up to you to protect it as best as possible. A few minutes every month will give protection.

• Have a recent pristine backup of the Registry
• Have two slightly older pristine backups of the Registry
Print details of how to restore it - you may be locked out!
• Know how to restore the Registry from your hard drive
• Know how to restore the Registry from a floppy disk
• Know your way around the Registry
• Make only one change at a time
• • • > All changes are final - there is no Undo < • • •

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Contents of the Registry under My Computer

HKEY_CLASSES_ROOT (files types, associations, interface, shortcuts, Drag-Drop)

HKEY_CURRENUSER (user profile information and customizations.
See also HKEY_USERS)
   SubKeys include
   AppEvents - sounds for system and application events
   Control Panel - settings
   InstallLocationsMRU - paths for Startup
   Keyboard - current settings
   Network - connection information
   RemoteAccess - Dial-up Networking location information
   Software - configuration for the current user


HKEY_LOCAL_MACHINE (hardware/software settings common to all users)
  SubKeys include
   Config - configuration and settings information
   Enum - hardware device information and settings
   Hardware - serial communication port information and settings
   Network - networks the user is currently logged onto
   Security - network security settings
   Software - software-specific information and settings
   System - system startup; device driver information; OS settings.

HKEY_USERS (desktop and user settings for individual users, if more than one)
HKEY_CURRENCONFIG (current hardware configuration)
HKEY_DYN_DATA (plug-n-play devices; changes dynamically)

You can right-click most entries, and edit them.

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Many would advise you to use a reliable utility to make changes to the Registry. Manual manipulation has been known to necessitate a complete re-installation, plus loss of data. Even if using a utility, you should backup the Registry first.

• Open Windows Explorer
• In the View menu, choose Options and enable Show all file types
Disable Hide MS-DOS file extensions, and click OK
• Highlight your Windows directory, and look in the right pane
• Copy the two files system.dat and user.dat, putting the copies in a different directory (on a separate physical drive, or partition, if you have one)
• Return to Options and disable Show all file types (this is the Windows 95/98 default)
• Repeat this procedure on a regular basic when, and only WHEN, your system is performing well.


If Windows 95/98 gives you the dreaded "Your registry is corrupt " message, it is telling you the Registry can not run, or can not continue to run even though Windows 95/98 loaded normally. The later may occur after installation of software or hardware.

Windows 95/98 keeps one backup copy of your Registry, created each and every time you launch Windows 95/98 (system.da0 and user.da0 in _:\Windows) i.e. it is a very recent backup of the Registry. If the 'corrupt' message occurs after a correct loading of Windows 95/98, then this backup should be usable. However if it occurs at loading time , then it is likely the Windows 95/98 backup is also corrupt and unusable.

There is no need to panic! Basically all you need do is reinstall your own pristine Registry backup. This will return your PC to exactly the way it was at the time you created the backup. Any alterations you made since that time will be lost (did one of them cause the problem?). You may have to reinstall recently installed programs - a lot easier than a full reinstallation of Windows 95/98, plus all programs and updates!


This assumes the Registry was saved to a directory called c:\regback\. - you must change this to point to your own backup directory.
    (the spaces you type in the following are important)

• Reboot computer to DOS (hit ALT+F5 during start up)
• At the DOS prompt type in cd windows and hit Enter
• Type in attrib -h -s -r system.dat and hit Enter
• Type in attrib -h -s -r user.dat and hit Enter
• Type in cd\ and hit Enter
• Type in copy c:\regback\system.dat c:\windows and hit Enter
• Type in copy c:\regback\user.dat c:\windows and hitEnter
• Restart Windows 95/98
Should this not work then repeat the above using an earlier backup.

98+In Windows 98 you can: Restart the computer to MS-DOS mode
Type in: scanreg /restore and press Enter. Restart your computer.
This will restore your Registry to its state when last successfully started


You may be locked out of Windows when you wish to re-install the Registry.

Unless you are blessed with total recall under stressful
conditions, you may wish to copy those instructions to
paper or floppy for future reference

Reinstalling the Registry from a floppy

Basically this is the same as above except the disk could also be a boot disk. Remember that the Registry files (system.dat and user.dat) will not fit on a floppy disk! Adjust the Pathways.

Note: You are likely to see A:\ on screen after bootup. Just type in C: and hit Enter to return to the hard drive.

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Microsoft no longer recommends Cfgback, the Registry backup utility that comes with Windows 95. It should not be used.

A large number of shareware utilities are available.

These include Quarter-deck's Cleansweep95, a good uninstaller and Registry editor.

See Microsoft's ERU (next section)

Emergency Recovery Utility ERU [1]

Microsoft's ERU can save you when hard disk problems or Registry corruption occur.

Microsoft recommends that you use the utility to create a backup each time you make any significant system changes, such as adding new hardware or software.

It is likely the two Registry files (system.dat and user.dat) will not fit on the same floppy - back them up to a different floppy AND the hard disk.

ERU will back up to a floppy the following important configuration files

• • msdos.sys • io.sys
• win.ini • system.ini • protocol.ini
• config.sys • autoexec.bat
• system.dat(Registry file)
• user.dat(Registry file)

Finding ERU

First open Windows Explorer
1. Insert and run the Windows 95 CD-ROM
2. Click on Browse This CD
3. Open the folder Other
4. Open the folder Misc
5. Locate and Drag the folder called ERU to the hard disk root Directory

Running ERU

1. Select Start • Run
2. Type in C:\eru and hit Enter
3. Follow the directions in the dialogue boxes.
If you prefer, you can locate the file eru.exe in the Windows directory and Drag a Shortcut on to the Desktop.

Recovering using ERU

1. Start your system using your ERU floppy disk
2. When you see Starting Windows 95, press the F8 key.
3. Select the Safe Mode Command Prompt Only option.
4. Type in erd at the prompt - program will replace all the corrupted files.
5. Remove the floppy, and re-start your computer in the normal manner.

CAUTION : Running ERU on a Windows 95 system that doesn't have a file listed in Eru.inf (located in the folder where you installed ERU) can lockup your machine!

CAUTION : While ERU seems a convenient backup method, this Site would NEVER rely on it. IF you want safety, then rely on yourself - make your own backup. Note: there have been reports that (earlier) versions of Win95 backed up System.1st instead of System.dat

Note: It is a GOOD IDEA to ensure you have CD-ROM drivers on all Startup disks.

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Please remember that you alone are responsible for the consequences of any changes you make to your computer hardware or software.

Copyright © LarryM 1998-2015